The yellow colour solution of $Na_2CrO_4$ changes to orange-red on passing $CO_2$ gas due to the formation of

In which of the following is the sporophyte parasitic on the gametophyte?

$A$ bullet is fired from a gun. The force on the bullet is given by $F = 600 - 2 \times 10^5 t$,where $F$ is in newton and $t$ is in second. The force on the bullet becomes zero as soon as it leaves the barrel. What is the impulse imparted to the bullet (in $N-s$)?

If a copper rod carries a direct current,the magnetic field associated with the current will be

When a tuning fork of frequency $341 \ Hz$ is sounded with another tuning fork,six beats per second are heard. When the second tuning fork is loaded with wax and sounded with the first tuning fork,the number of beats is two per second. The natural frequency of the second tuning fork is (in $Hz$)

Which set of elements forms stable,covalently bonded hydrogen-bonded hydrides?